libbpf: Correct bpf_core_read.h comment wrt bpf_core_relo struct

Past commit ([0]) removed the last vestiges of struct bpf_field_reloc,
it's called struct bpf_core_relo now.

  [0] 28b93c64 ("libbpf: Clean up and improve CO-RE reloc logging")
Signed-off-by: Dima Tisnek <dimaqq@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20240121060126.15650-1-dimaqq@gmail.com

tools/lib/bpf/bpf_core_read.h

@@ -268,7 +268,7 @@ enum bpf_enum_value_kind {
  * a relocation, which records BTF type ID describing root struct/union and an
  * accessor string which describes exact embedded field that was used to take
  * an address. See detailed description of this relocation format and
- * semantics in comments to struct bpf_field_reloc in libbpf_internal.h.
+ * semantics in comments to struct bpf_core_relo in include/uapi/linux/bpf.h.
  *
  * This relocation allows libbpf to adjust BPF instruction to use correct
  * actual field offset, based on target kernel BTF type that matches original